In this publication, the cooling fluid for direct oil-cooled electric traction drive is investigated. A dedicated thermal resistance model was developed in order to show the influence of the fluid properties on the continuous performance. For this purpose, the heat transfer parameters are adjusted in the simulation using an exponential approach in order to evaluate the cooling fluid. In a sensitivity study, density, heat capacity, thermal conductivity, and viscosity are investigated. Because viscosity, within the range investigated, shows the largest percentage deviation from the reference fluid, the greatest effect on performance can be seen here. In order to check the plausibility of the calculated results of the thermal simulation, two fluids were chosen for performance testing on a dedicated electro motor cooling (EMC) test. Beyond the investigation of heat transfer, aging of the defined fluid at maximum heat input over several hours is also evaluated. Only slight changes of the fluid properties are detected. This publication presents a thermal model for direct oil-cooled drive trains, which consider fluid properties. Furthermore, the model was tested for plausibility on real hardware.

Due to the auxiliary loads' increasing influence on the overall energy consumption of electrified vehicles, a holistic tank‐to‐wheel analysis is necessary. To do so, the impact of the auxiliary load on the energy consumption of a fuel cell electric vehicle (FCEV) drivetrain is investigated by taking different driving behaviors and three European environmental conditions (Spanish, German and Norwegian weather profiles) into account. The driving pattern is analyzed with the study ‘Mobilität in Deutschland' [1] and represented with the Artemis driving cycles [2]. To match various situations of the everyday life, realistic boundary conditions are determined by five starting times. The corresponding weather conditions are obtained and five weather profiles for every meteorological season including the ambient temperature, solar flux and humidity are considered. By using a complete FCEV simulation model, a realistic energy consumptions is simulated and the impact of different climate conditions as well as driving behaviors is investigated. As a result, a significant influence of the auxiliary load on the overall energy consumption is detected and the need to consider the overall energy demand is demonstrated.

The thermal design of electrical machines has numerous influencing factors. This paper compares different cooling methods, their volume flow rates and other machine parameters with regard to the continuous power of a PMSM. Understanding the characteristics of different heat sinks depending on their operating point is important for an expedient design in order to avoid derating due to overtemperatures. As a design guideline, this contribution shows the influence of stator cooling jackets, rotor shaft cooling and direct end winding cooling for different machine lengths and volume flow rates. Both water and oil are investigated as coolants. With increasing machine dimensions, end winding cooling becomes less effective for heat sources in the center of the machine while the heat transferred in the cooling jacket increases. A sensitivity study of other machine parameters, such as the maximum allowed magnet temperature or the coolant inlet temperature, improves the understanding of the reader as to how the continuous power of a PMSM can be increased when the rotor temperature limits the performance.